Fluorescent lamp which have a higher degree of efficiency and a longer operating life compared with an incandescent lamp, have been widely used as an alternative light source to replace incandescent lamp. Moreover, recently, in addition to conventionally used fluorescent lamps, electrodeless fluorescent lamps have been put to practical use and been under development. These electrodeless fluorescent lamps are also commonly known as electromagnetic induction lamps or simply induction lamps. Many electrodeless fluorescent lamps rely for operation on the presence of mercury in the lamp envelope. Most of them use solid mercury or mercury amalgam.
In this form, the mercury is compounded with other metals, similar to the amalgam once widely used in dental fillings. It will not release toxic mercury vapor when exposed to room temperature and poses no threat of contamination. The use of amalgam, aside from eliminating the risk of mercury contamination is also used to regulate the mercury vapor pressure inside the lamp vessel that will ultimately affect the lamp efficiency. The amalgam can also be easily recovered in the case of lamp breakage and simpler to recycle at end of lamp life.
Electrodeless fluorescent lamps typically include at least one slender tube that has an opening into the interior of the lamp envelope and which, in construction of the lamp, is used as an exhaust and fill conduit. The mercury amalgam is typically placed inside this exhaust tube prior to the tube being hermetically sealed at completion of manufacture. This presents a problem especially when the lamp is mounted in a direction such that the opening of the exhaust tube is pointed downwardly. In certain instances when the amalgam melts or disintegrates, it tended to drop by gravity into the interior of the lamp envelope where it can cause changes in the lumen output and the lumen temperature performance of the lamp, which ultimately reduces the lifetime of the lamp.
The limited mounting direction becomes a hindrance in the widespread use of electrodeless fluorescent lamps despite its many superior properties. There is thus required a means for retaining and preventing the amalgam from going inside the lamp envelope regardless of mounting direction. A look into the prior arts discovered multiple patents that might be relevant. However, none of them possesses the novelty of the instant invention.